brain metastasis from differentiated thyroid carcinoma responding to radioiodine therapy

Brain metastasis (bm) occurs only in about 1% of differentiated thyroid carcinoma (dtc) cases. although dtc generally has a good prognosis, once bm develops, the mortality rate significantly increases up to 78%. bm is usually treated by surgical resection or external radiotherapy, whereas radioactive iodine therapy (rait) using i-131 is much less often chosen because bm often shows poor uptake of i-131. in addition, even in case i-131 accumulates in the bm, rait could cause adverse effects such as brain hemorrhage and cerebral edema.we present a case of bm from dtc that showed response to i-131 therapy with no severe adverse effects. the brain lesion was very small and asymptomatic, and was only found after a post-therapy i-131 scintigraphy. there are a few case reports where bm was cured by rait with little to no side effects. we theorize that bm that is small in size, asymptomatic and show i-131 accumulation could be successfully treated with rait.